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1
Bennett, M. A. "Charge exchange between light ions." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355835.
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2
Easa, S. I. "Charge exchange process in atom-surface scattering." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376837.
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3
Park, Hojoon Timothy. "Pion single charge exchange on the deuteron." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32657.
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4
Gregory, Nikolas K. "Pion single charge exchange on the deuteron." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32675.
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5
Forster, Christine. "Aspects of charge exchange in ion-atom collisions." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6189/.
Testo completoAbstract (sommario):
The straight line semi-classical Impact Parameter method has been modified for use with classical trajectories. Ion-atom collisions have been modelled using wavefunctions expanded in terms of atomic basis states which were centred on either the target or projectile ions. Total and differential charge exchange cross-sections are presented for (^4)He(^++) and (^4)He(^+) collisions within the centre of mass energy range 0.21 kev < E(_em) < 2.5 keV. Results using curved and straight line paths are compared with data from other authors. Significant trajectory effects were found at the lower energies in the range. The curved trajectory results were lower than those from the straight line model and also lower than previous calculations carried out. At higher energies in the range there was good agreement between straight line and curved trajectory models and previous work. Differential cross-sections were found to be sensitive to the trajectories employed, and comparisons have been made with previous work. Total, state specific and differential cross- sections for charge exchange are presented for Be(^++) and H collisions using a five state basis, within the centre of mass energy range 0.111 keV < E(_em) < 0.4444 keV. There was reasonable agreement between the straight line results and previous work. There were significant trajectory effects for all the final charge transfer states. Results are presented for low-energy collisions between positively charged muons and atomic hydrogen. An eight state basis has been used. Direct excitation cross sections for n = 2 atomic states and charge transfer cross sections to Is and n = 2 have been calculated. The effect on the cross sections of using different internuclear potentials has been examined. Trajectory effects were small for charge transfer to Is but were more pronounced in the direct excitation and charge exchange cross- sections to n = 2. These results have been compared to those obtained for curved trajectory H(^+) and H collisions at the same relative velocity, to assess the validity of velocity scaling. It was found that velocity scaling was reliable for charge transfer to Is and for total electron capture cross-sections. However, it was progressively inaccurate for direct excitation and for electron capture into excited states for µ(^+) impact energies of less than 300 eV. These results are discussed and suggestions for further work are made.
6
Nijs, Gerardus de. "Pathways to charge equilibration following multiple electron exchange between highly charged ions and atoms." [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1996. http://irs.ub.rug.nl/ppn/148625770.
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7
Rugmai, Supagorn. "Three-body models of breakup and charge-exchange reactions." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/843216/.
Testo completoAbstract (sommario):
We formulate and apply a three-body Glauber model and an adiabatic theory, as alternative approaches to the DWBA method, to study breakup and charge exchange reactions of loosely bound nuclei. The theories derive full finite-range transition amplitudes, which incorporate three-body effects. The formulated Glauber three-body breakup transition amplitude is applied to the (d, pn) deuteron breakup reaction. Three-body s-wave breakup calculations are performed to analyse 260 MeV 63Cu(d, pn) and 270 MeV 12C(d, pn) reaction differential cross-section data. The calculations describe the data fairly well, for low p-n relative energies. The adiabatic theory, in a special limit, is applied to enable computational checks of the Glauber three-body breakup calculations, and for estimation of non-s-wave breakup contributions to the (d, pn) reaction. An adiabatic theory of Coulomb breakup is presented which derives a closed-form adiabatic transition amplitude for Coulomb breakup. Calculations describe deuteron breakup at forward angles at 56, 140 and 270 MeV reasonably well. Previous DWBA analyses are also discussed, and assumptions made in those DWBA calculations are discussed critically. The three-body Glauber model is extended to study the (d, pp) charge-exchange reaction. Three-body effects in the 12C(d, pp)12B reaction are investigated by comparing Glauber calculations with their DWBA limits. The results indicate that these three-body effects are significant and might be responsible for ad hoc modifications needed in DWBA analyses of the same reaction.
8
Ng, Hui-Siong. "Low energy (K§+, ¹²C) charge exchange cross section measurements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ60159.pdf.
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9
Müllers, Andreas [Verfasser]. "Production of antihydrogen via double charge exchange / Andreas Müllers." Mainz : Universitätsbibliothek Mainz, 2013. http://d-nb.info/1033733016/34.
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10
Spence, J. "Studies of charge exchange recombination in laboratory fusion plasmas." Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382408.
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11
Laperle, Christopher Michael. "Experimental studies of multi-body dissociative charge exchange dynamics /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3153693.
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12
Hessey, Nigel P. "The pion double charge exchange reaction on ¹⁸O at 50 MeV." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24682.
Testo completoAbstract (sommario):
This thesis discusses the pion double charge exchange (DCX) reaction ¹⁸0(π⁺,π⁻)¹⁸Ne at 50 MeV. Transitions to the ground state of ¹⁸Ne, which is the double-isobaric-analogue state (DIAS) of ¹⁸0, have been isolated. The differential cross sections for DIAS transitions have been measured at 6 scattering angles from 18.2° to 122.6°. The experiment was performed at TRIUMF in December 1984 using the QQD low energy pion spectrometer [26].
The differential cross section angular distribution is forward peaked, falling from 4.7±0.5 μb/sr at 0° (by extrapolation) to 0.61±0.11 μb/sr at 122.6°. The total (angle-integrated) cross section is 16.2±1.2 μb.
DCX measurements are expected to give information on nuclear structure that is hard to obtain by other reactions. This information includes short range correlations and neutron-proton density differences. However, before such information can be extracted the mechanism for DCX must be understood. The aim of this experiment was to provide more data to test the various theories of the DCX mechanisms. The implications of the results for several theories of DCX are discussed.
The forward peaking of DCX angular distributions at 50 MeV was unexpected. 50 MeV single charge exchange (SCX) angular distributions are forward dipped e.g. [14], a result of the cancellation of the 0° s and p wave scattering amplitudes for the reaction p(π⁺,π⁰)n. Early DCX calculations were based on the simple sequential mechanism. This assumes DCX proceeds via 2 successive SCX reactions, with the isobaric analogue as the intermediate state. These calculations predicted forward dipping and small cross sections for DCX [13,15]. The data shows this mechanism is an over-simplification.
The standard model for π-nucleus scattering is the optical potential. Johnson and Siciliano are developimg a potential with which to calculate elastic, SCX and DCX cross sections [48,38,22]. They include second, order terms, important in DCX because the reaction must involve scattering by at least two nucleons. By using a general form for the optical potential they include contributions from excited intermediate states.
Miller has suggested the forward peaking is due to the presence of six-quark clusters in the nucleus [16]. His model reproduces the data for 50 MeV DCX on ¹⁸0 and ¹⁴C at forward angles.
Karapiperis and Kobayashi have used the Δ-hole model to calculate elastic, SCX and DCX cross sections [19]. They obtain fair agreement with data for a range of nuclei and energies.
Jennings et al. [22] are developing a model in which short range correlations produce the forward peaking. This work is at an early stage.
More DCX measurements are needed to choose between the various models. Measurements at 50 MeV are particularly valuable because the simple sequential mechanism is small, allowing other mechanisms to be observed. Further data such as excitation functions below 80 MeV and angular distributions for other nuclei are needed.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate
13
Liang, H. "Nuclear charge-exchange excitations in a self-consistent covariant approach." Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00506913.
Testo completoAbstract (sommario):
Les excitations d'´echange de charge dans les noyaux constituent l'un des sujets importants et actuels en physique nucl´eaire et en astrophysique. En principe, une connaissance syst´ematique de l'´evolution du comportement de ces excitations `a travers la table des ´el´ements fournirait des informations directes sur les propri´et´es en spin et isospin de l'interaction entre nucl´eons dans le milieu nucl´eaire, et sur l'´equation d'´etat de la mati`ere nucl´eaire. Par ailleurs, une quantit´e d'importance essentielle pour la structure des noyaux, l'´epaisseur de la peau de neutrons, peut ˆetre d´etermin´ee par la r`egle de somme de la r´esonance spin-dipolaire (RSD) ou par la s´eparation en ´energie entre l'´etat isobarique analogue (EIA) et la r´esonance de Gamow-Teller (RGT). Plus g´en´eralement, les excitations d'´echange de charge permettent d'aborder des probl`emes d'int´erˆet g´en´eral tels que l'´etude de l'´evolution des ´etoiles `a neutrons et des supernovae, la d´ecroissance β des noyaux le long du processus r dans la nucl´eosynth`ese stellaire, ou les interactions neutrino-noyau. Elles jouent aussi un rˆole essentiel pour extraire la valeur de l'´el´ement Vud de la matrice de Cabibbo-Kobayashi- Maskawa par le biais de la r´eaction de d´ecroissance β super-permise 0+ → 0+ dans les noyaux. Pour toutes ces raisons, il est important de d´evelopper des th´eories microscopiques des excitations d'´echange de charge, et ceci constitue la principale motivation de notre recherche. Dans ce travail, nous ´etablissons le formalisme et les m´ethodes num´eriques pour d´ecrire les excitations d'´echange de charge dans le cadre de la Random Phase Approximation (RPA) selfconsistante construite sur l'approximation de Hartree-Fock relativiste (RHF). Un test important de pr´ecision num´erique est r´ealis´e sur l'´etat isobarique analogue. La m´ethode est ensuite utilis´ee pour mener des applications num´eriques r´ealistes sur un certain nombre de questions physiques: les r´esonances de spin-isospin dans les noyaux proches des noyaux magiques, les corrections dˆues aux m´elanges d'isospin dans les transitions β super-permises, les interactions neutrino-noyau dans les voies de courants charg´es. Pour les deux modes importants de spin-isospin que sont la RGT et la RSD nous trouvons qu'un excellent accord avec l'exp´erience est obtenu sans aucun r´eajustement des param`etres du mod`ele. De plus, les termes d'´echange de l'interaction induite par les m´esons isoscalaires jouent un rˆole essentiel dans les excitations de spin-isospin, `a la diff´erence de la RPA construite sur l'approximation de Hartree relativiste. En ce qui concerne notre ´etude des transitions β 0+ → 0+ super-permises l'une des conclusions est que les corrections δc dˆues aux violations de la sym´etrie d'isospin d´ependent sensiblement du champ moyen d'´echange produit par les interactions coulombiennes, mais ne changent pas sensiblement avec le mod`ele de Lagrangien utilis´e. Nous utilisons ces valeurs de δc pour d´eduire des plus r´ecentes valeurs exp´erimentales de ft dans les noyaux T = 1, et en tenant compte des corrections radiatives, les valeurs de Ft ”ind´ependantes de noyaux”. Nous obtenons ainsi des valeurs de l'´el´ement de matrice |Vud| de Cabbibo-Kobayashi-Maskawa en bon accord avec les valeurs d´eduites des d´ecroissances neutronique et pionique, et les transitions dans les noyaux miroirs, tandis que la somme des carr´es des ´el´ements de la premi`ere ligne d´evie l´eg`erement de la condition d'unitarit´e. Nous avons ´egalement utilis´e nos fonctions d'onde RPA pour ´evaluer les amplitudes de transition correspondant `a l'interaction faible lepton-hadron sous la forme standard courant-courant. Ainsi, les processus faibles semi-leptoniques tels que les r´eactions neutrino-noyau, capture leptonique charg´ee, d´esint´egration β, peuvent ˆetre ´etudi´es. Nos premi`eres applications concernent la r´eaction 16O(νe, e−)16F pour laquelle nous comparons nos pr´edictions avec celles d'autres auteurs. Dans la discussion des r´esultats nous nous effor¸cons en particulier de clarifier l'influence appr´eciable des diff´erentes prescriptions que l'on peut adopter pour le choix de la constante de couplage vecteur axiale et l'inclusion ou non des ´etats excit´es de basse ´energie dans le noyau final.
14
Liang, Haozhao. "Nuclear charge-exchange excitations in a self-consistent covariant approach." Paris 11, 2010. http://www.theses.fr/2010PA112178.
Testo completoAbstract (sommario):
Les excitations d'échange de charge dans les noyaux constituent l'un des sujets importants et actuels en physique nucléaire et en astrophysique. En principe, une connaissance systématique de l'évolution du comportement de ces excitations à travers la table des éléments fournirait des informations directes sur les propriétés en spin et isospin de l'interaction entre nucléons dans le milieu nucléaire, et sur l'équation d'état de la matière nucléaire. Par ailleurs, une quantité d'importance essentielle pour la structure des noyaux, l'épaisseur de la peau de neutrons, peut être déterminée par la règle de somme de la résonance spin-dipolaire (RSD) ou par la séparation en énergie entre l'état isobarique analogue (ElA) et la résonance de Gamow-Teller (RGT). Plus généralement, les excitations d'échange de charge permettent d'aborder des probèmes d'inérêt général tels que l'étude de l'évolution des étoiles à neutrons et des supernovae, la décroissance des noyaux le long du processus r dans la nucléosynthèse stellaire, ou les interactions neutrino-noyau. Elles jouent aussi un rôle essentiel pour extraire la valeur de l'élément Vud de la matrice de Cabibbo-Kobayashi-Maskawa par le biais de la réaction de décroissance β super-permise 0 +→ 0+ dans les noyaux. Pour toutes ces raisons, il est important de d'evelopper des théories microscopiques des excitations d'échange de charge, et ceci constitue la principale motivation de notre recherche. Dans ce travail, nous établissons le formalisme et les méthodes numériques pour d' ecrire les excitations d'échange de charge dans le cadre de la Random Phase Approximation (RPA) self-consistante construite sur l'approximation de Hartree-Fock relativiste (RHF). Un test important de précision numérique est réalisé sur l'état isobarique analogue. La méthode est ensuite utilisée pour mener des applications numériques réalistes sur un certain nombre de questions physiques : les résonances de spin-isospin dans les noyaux proches des noyaux magiques, les corrections dûes aux mélanges d'isospin dans les transitions β super-permises, les interactions neutrino-noyau dans les voies de courants chargés. Pour les deux modes importants de spin-isospin que sont la RGT et la RSD nous trouvons qu'un excellent accord avec l'expérience est obtenu sans aucun réajustement des paramètres du modèle. De plus, les termes d'échange de l'interaction induite par les mésons isoscalaires jouent un rôle essentiel dans les excitations de spin-isospin, à la différence de la RPA construite sur l'approximation de Hartree relativiste. En ce qui concerne notre étude des transitions β 0+ → 0+ super-permises, l'une des conclusions est que les corrections δc dues aux violations de la symétrie d'isospin dépendent sensiblement du champ moyen d'échange produit par les interactions coulombiennes, mais ne changent pas sensiblement avec le modèle de Lagrangien utilisé. Nous utilisons ces valeurs de δc pour déduire des plus récentes valeurs expérimentales de ft dans les noyaux T = 1, et en tenant compte des corrections radiatives, les valeurs de Ft "indépendantes de noyaux". Nous obtenons ainsi des valeurs de l'élément de matrice ıVudı de Cabbibo-Kobayashi-Maskawa en bon accord avec les valeurs déduites des décroissances neutronique et pionique, et les transitions dans les noyaux miroirs, tandis que la somme des carrés des éléments de la première ligne dévie légèrement de la condition d'unitarité. Nous avons également utilisé nos fonctions d'onde RPA pour évaluer les amplitudes de transition correspondant à l'interaction faible lepton-hadron sous la forme standard courant-courant. Ainsi, les processus faibles semi-leptoniques tels que les réactions neutrino-noyau, capture leptonique chargée, désintégration β , peuvent être étudiés. Nos premières applications concernent la réaction 16 O(Ve , e - ) 16 F pour laquelle nous comparons nos prédictions avec celles d'autres auteurs. Dans la discussion des résultats nous nous efforçons en particulier de clarifier l'influence appréciable des différentes prescriptions que l'on peut adopter pour le choix de la constante de couplage vecteur axiale et l'inclusion ou non des états excités de basse énergie dans le noyau final<br>Nowadays, charge-exchange excitations in nuclei become one of the central topics in nuclear physics and astrophysics. Basically, a systematic pattern of the energy and collectivity of these excitations could provide direct information on the spin and isospin properties of the in-medium nuclear interaction, and the equation of state of asymmetric nuclear matter. Furthermore, a basic and critical quantity in nuclear structure, neutron skin thickness, can be determined indirectly by the sum rule of spin-dipole resonances (SOR) or the excitation energy spacing between the isobaric analog states (lAS) and Gamow-Teller resonances (GTR). More generally, charge-exchange excitations allow one to attack other kinds of problems outside the realm of nuclear structure, like the description of neutron star and supernova evolutions, the β-decay of nuclei which lie on the r-process path of stellar nucleosynthesis, and the neutrino-nucleus cross sections. They also play an essential role in extracting the value of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vud via the nuclear 0+→ 0 + superallowed Fermi β decays. For all these reasons, it is important to develop the microscopic theories of charge-exchange excitations and it is the main motivation of the present work. Ln this work, a fully self-consistent charge-exchange relativistic random phase approximation (RPA) based on the relativistic Hartree-Fock (RHF) approach is established. Its self-consistency is verified by the so-called lAS check. This approach is then applied to investigate the nuclear spin-isospin resonances, isospin symmetry-breaking corrections for the superallowed β decays, and the charged-current neutrino-nucleus cross sections. For two important spin-isospin resonances, GTR and SOR, it is shown that a very satisfactory agreement with the experimental data can be obtained without any readjustment of the energy functional. Furthermore, the isoscalar mesons are found to play an essential role in spin-isospin resonances via the exchange terms, which leads to a profound effect in the nuclear isovector properties, e. G. , the density dependence of the symmetry energy in nuclear matter. Ln the investigation of the isospin symmetry-breaking corrections for the superallowed β decays, it is found that the corrections δc are sensitive to the proper treatments of the Coulomb mean field, but not so much to specific effective interactions. With these corrections δc, the nucleus-independent Ft values are obtained in combination with the experimental ft values in the most recent survey and the improved radiative corrections. The values of Cabibbo-Kobayashi-Maskawa matrix element IVudI thus obtained weil agree with those obtained in neutron decay, pion decay, and nuclear mirror transitions, while the sum of squared top-row elements somehow deviates from the unitarity condition. Expressing the weak lepton-hadron interaction in the standard current-current form, the relevant transitions from the nuclear ground state to the excited states are calculated with RHF+RPA approach. Ln this way, the semileptonic weak interaction processes, e. G. , neutrino reactions, charged- lepton capture, β-decays, can be investigated microscopically and self-consistently. First illustrative calculations of the inclusive neutrino-nucleus cross section are performed for the 16 O(Ve ,e-)16 F reaction, and a good agreement with the previous theoretical studies is obtained. The main effort is dedicated to discussing the substantial influence of different recipes for the axial vector coupling strength and the theoretical low-Iying excited states of the daughter nucleus
15
Morris, Bradford Shepherd J. E. Shepherd J. E. "Charge-exchange collision dynamics and ion engine grid geometry optimization /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-02282007-154751.
Testo completo
16
MAGANA, VSEVOLODOVNA RUSLAN IDELFONSO. "Transfer reactions, neutrinoless double beta decay and double charge exchange." Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/930766.
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17
Renfrow, Steven N. (Steven Neal). "Charge State Distributions in Molecular Dissociation." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc278340/.
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18
Li, Debin. "Exploring electron transfer in myoglobin-based transistors." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10211.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2009.<br>Title from document title page. Document formatted into pages; contains xiii, 104 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 99-104).
19
Yoon, Kwansik. "The effect of the electrode composition on electron transfer through an electroactive monolayer." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=771.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 1999.<br>Title from document title page. Document formatted into pages; contains xi, 96 p. : ill. (some col.) Includes abstract. Includes bibliographical references.
20
Davies, Peter George. "Charge exchange in ion-atom collisions relevant to fusion plasma diagnostics." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4740/.
Testo completoAbstract (sommario):
Total charge exchange and excitation cross-sections are presented for collisions between He(^2+) ions and helium atoms, the laboratory frame collision energy being in the range 16-800keV. Cross-sections from the helium ground state and the He(ls2s(^1)S) and He(ls2s(^3)S) metastable states are calculated. The calculations were performed using the semiclassical impact parameter model where wave-functions are expressed as an expansion of two-electron atomic basis states. Transfer channels included plane-wave translation factors. The transition He(^+)(n = 4) → He(^+)(n = 3) results in the emission of visible light (468.5nm) which is observed in the JET fusion device. Helium beam injection into the JET device introduces some of the atoms in initially excited states. Even a small fraction of metastable helium effects the observed 468.5nm spectrum significantly because of the very large charge exchange cross-sections. Accurate charge exchange cross-sections to the He(^+)(n = 4) states are required to analyse the spectroscopic data used in the diagnosis of the plasma. The cross-sections produced are therefore also presented in a form suitable for direct inclusion into the plasma analysis database. Where possible the current results are compared to previous calculations. Total charge exchange cross-sections from the He(ls2s(^1)S) state are in good agreement with the previous one-electron calculation. Charge exchange cross-sections from the triplet state are found to differ with those from the singlet. The results are discussed in the context of their usefulness in the diagnosis of fusion plasmas. Suggestions for further work are made.
21
Dowell, Marla L. (Marla Lorraine) 1965. "Pion single charge exchange in three body nuclei at intermediate energies." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/26856.
Testo completo
22
Kabutz, Rudolf T. "The (p, n) charge-exchange reaction on ⁹⁰Zr at intermediate energies." Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/17385.
Testo completoAbstract (sommario):
Bibliography: p. 67-69.<br>Using the Time-of-Flight facility at the National Accelerator Centre at Faure, the (p, n) charge-exchange reaction has been studied at intermediate energies of 120, 160 and 200 MeV, and at angles of 0°, 2° and 4°. In this work the data collected for the ⁹⁰Zr target will be presented. The influence on the data from slow neutrons due to previous pulses is discussed and the best manner of removing them from the spectra is recommended. It is shown how the background cosmic rays can be utilised to measure the intrinsic resolution of the detectors and to obtain an estimate of the neutron energy threshold. The differential cross-sections for the states corresponding to Fermi and Gamow-Teller transitions were extracted from the time spectra. The sum of the strength of all the discrete Gamow-Teller states was determined and compared to the Ikeda Sum Rule. It was found that only 50% of the sum could be accounted for in the discrete states. An overview of the theory that has been developed to extract Gamow-Teller strengths from the (p, n) cross-sections is given. Some of the theoretical models that have been used to describe the ⁹⁰Zr(p, n)⁹⁰ Nb reaction and account for the missing Gamow-Teller strength are briefly discussed.
23
Otto, E., S. Rubbert, and J. Borrmeister. "Thermodynamics and charge exchange of the new BMW six-cylinder engine." Sage, 2000. https://publish.fid-move.qucosa.de/id/qucosa%3A38437.
Testo completoAbstract (sommario):
The BMW in-line six-cylinder engine has been modified and introduced to production in the new BMW 3 Series model. Its major features include variable intake and exhaust camshaft timing, a new induction system with resonance charging, a turbulence-generating system in the intake ports and a new exhaust system with two closed-loop, coupled catalysts integrated into the exhaust manifold. The cam timing of both camshafts can be adjusted continuously within a range of 40° crank angle (CA) for the inlet cams and 25° CA for the exhaust cams. The turbulence-generating system supplies combustion air to the engine during part load operation and produces the necessary charge motion to run the engine with greater valve overlap at low loads and speeds. Its combination with variable camshaft timing results in lower fuel consumption and exhaust emissions that meet the LEV emission standard. In addition, the variable cam timing raises the torque curve of the unthrottled engine, particularly at low engine speed. The maximum values for torque and power output are unchanged, but maximum torque is reached 500 r/min earlier than with the previous engine.
24
Unal, Asuman. "Ion-exchange and charge transport in films of conducting polymer and composite." Thesis, University of Leicester, 2017. http://hdl.handle.net/2381/40867.
Testo completoAbstract (sommario):
This thesis was concerned with the improvement of novel modified electrodes based on polyaniline (Pani) and its copolymers with o-aminophenol (o-AP) and o-toluidine (o-OT) and the investigation of their defluoridation properties, and further with the enhancement of the charge transport of Pani and polypyrrole (PPy) via multiwall carbon nanotubes (MWCNTs) in Ethaline. The principle of electrochemical ion-exchange modified electrodes is based on the doping/dedoping process of conducting polymer films. This feature makes it possible to remove undesirable ions, such as fluoride, from aqueous solution. The fabrication of Pani and its copolymers with o-AP/o-OT, carried out under optimal conditions by EQCM, gave an excellent opportunity to test for the removal of fluoride ions at pH 6.60 from water without chemical contamination of the copolymer. Pani, and its copolymers with o-AP/o-OT, poly(aniline-co-o-aminophenol) (Pani-PAP) and poly(aniline-co-o-toluidine) (Pani-POT), can theoretically take up about 91.2 mg g-1 fluoride ions per redox site of polymer film. Experiments indicated that the Pani, Pani-PAP and Pani-POT films removed 51.6 ± 1.0 mg g-1, 65.0 ± 0.6 mg g-1 and 66.8 ± 1.8 mg g-1, respectively, of fluoride ions per redox site of each (co)polymer film. This demonstrates that the copolymerisation of aniline with its derivatives enhanced the defluoridation properties of Pani. Pani and PPy are also promising materials for energy storage devices. The presence of MWCNTs to some extent enhanced both the electrochemical properties and mechanical stability in Ethaline, which maintains high efficiency and high-quality depositions through the use of the EQCM technique. The specific mass capacitances of these composite films were determined to be 1170.1 ± 44.7 F g-1 and 120.5 ± 5.4 F g-1 for Pani/MWCNTs and PPy/MWCNTs, respectively.
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Wang, Mark Yu Da 1965. "Inclusive pion single charge exchange in 4He in the [delta]-resonance region." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11693.
Testo completoAbstract (sommario):
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1994.<br>On t.p., "[delta]" appears as the upper-case Greek letter. Vita.<br>Includes bibliographical references (leaves 173-178).<br>by Mark Yu Da Wang.<br>Sc.D.
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Manzo, Michele. "Engineering ferroelectric domains and charge transport by proton exchange in lithium niobate." Doctoral thesis, KTH, Kvantelektronik och -optik, QEO, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-162269.
Testo completoAbstract (sommario):
Ferroelectrics are dielectric materials possessing a switchable spontaneous polarization, which have attracted a growing interest for a broad variety of applications such as ferroelectric lithography, artificial photosynthesis, random and dynamic access memories (FeRAMs and DRAM), but also for the fabrication of devices for nonlinear optics, etc. All the aforementioned applications rely on the control of the ferroelectric domains arrangement, or the charge distribution and transport. In this regard, the main prerequisite is the engineering of the spontaneous polarization, obtained by reversing its orientation or locally inhibiting it. In the latter case, the interface created by the spatial discontinuity of the spontaneous polarization generates local charge accumulation, which can be used to extend the capabilities of ferroelectric materials. This thesis shows how engineering the spontaneous polarization in lithium niobate (LN) by means of proton exchange (PE), a temperature-activated ion exchange process, can be used to develop novel approaches for ferroelectric domain structuring, as well as fabrication of self-assembled nanostructures and control of ionic/electronic transport in this crystal. In particular, it is shown how the electrostatic charge at PE:LN junctions lying below the crystal surface can effectively counteract lateral domain broadening, which in standard electric field poling hampers the fabrication of ferroelectric gratings for Quasi-Phase Matching with periods shorter than 10 μm. By using such an approach, ferroelectric gratings with periods as small as ~ 8 μm are fabricated and characterized for efficient nonlinear optical applications. The viability of the approach for the fabrication of denser gratings is also investigated. The charge distribution at PE:LN junctions lying on the crystal surface is modelled and used to drive the deposition of self-assembled nanowires by means of silver photoreduction. Such a novel approach for PE lithography is characterized for different experimental conditions. The results highlight a marked influence of the orientation of the spontaneous polarization, the deposition times, as well as the reactants concentrations and the doping of the substrate with MgO. Based on the fact that proton exchange locally reduces the spontaneous polarization, a quick and non-destructive method for imaging PE regions in lithium niobate with nanoscale resolution is also developed by using Piezoresponse Force Microscopy. Moreover the relative reduction of the piezoelectric d33 coefficient associated to PE is estimated in lithium niobate substrates with and without MgO-doping. Finally, by using advanced Scanning Probe Microscopy techniques, the features of charge transport in PE regions are further investigated with nanoscale resolution. A strong unipolar response is found and interpreted in light of ionic-electronic motion coupling due to the interplay of interstitial protons in the PE regions, nanoscale electrochemical reactions at the tip-surface interface, and rectifying metal-PE junctions.<br><p>QC 20150325</p>
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唐素明 and So-ming Glenna Tong. "Theoretical studies of transition metal containing diatomics and DNA electron transfer." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31244828.
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Brevnov, Dmitri A. "Development and application electrochemical and spectrophotometric methods based upon AC potential modulation for characterization of hybrid bilayer membranes and electroactive self-assembled monolayers supported on gold electrodes." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1462.
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Tsang, Chun-kit. "Pathway analysis on electron transfer in ruthenium modified cytochrome C." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B22718898.
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Fong, Wilson. "Inclusive pion double charge exchange in light p-shell nuclei at intermediate energies." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/26854.
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Forte, Vincenzo. "Performance of the CERN PSB at 160 MeV with H- charge exchange injection." Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22701/document.
Testo completoAbstract (sommario):
Dans le cadre du projet LIU, vise à augmenter la puissance des injecteurs du LHC, le CERN PS Booster (PSB) sera mis à jour avec un système d'injection d'échange de charge H- et son énergie d'injection sera portée de 50 MeV à 160 MeV pour obtenir la luminosité du faisceau nécessaire pour le LHC High-Luminosity Upgrade. Effets de charge d'espace comme pertes de faisceau et incrément d’émittance transversale à l'injection vont être les principales limites vers la réalisation de la haute luminosité souhaitée. Des études sur la dynamique du faisceau en présence de charge d'espace afin d'évaluer les performances du PSB après la mise à niveau ont été effectuées. La première partie du travail consiste de mesures dans la présente machine, pour étudier les effets de charge d'espace et son interaction avec les résonances et d'avoir un ensemble de données pour le code benchmarking. Le code choisi pour le suivi du faisceau en présence de charge d'espace est PTC-Orbit (et PyOrbit). Les études de convergence numériques nécessaires sont présentées conjointement avec les études de la comparaison des simulations avec les mesures dans la machine. Une fois évalué le code et ses limites, les prévisions pour l'injection dans le PSB à 160 MeV avec des poutres de luminosité élevé sont livrés en termes de pertes de faisceau et incrément d’émittance. Ces études comprennent l'optimisation du point de fonctionnement, la compensation des résonances et/ou la correction de chromaticité en tenant compte des erreurs magnétiques attendus dans la machine<br>As part of the LHC Injector Upgrade Project, the CERN PS Booster (PSB) will be upgraded with a H- charge exchange injection system and its injection energy will be raised from 50 MeV to 160 MeV to obtain the beam brightness required for the LHC High-Luminosity Upgrade. Space charge effects like beam losses and transverse emittance blow-up at injection are expected to be the main limitations towards the achievement of the required high brightness. Studies of beam dynamics in presence of space charge in order to evaluate the performances of the PSB after the Upgrade have been performed. The first part of the work consists of measurements in the present machine, to study the effects of space charge and its interplay with resonances and to have a good set of data for code benchmarking. The code chosen for the beam tracking in presence of space charge is PTC-Orbit (and PyOrbit). Necessary numerical convergence studies are presented together with a benchmark with the PSB measurements. Once assessed the code and its limitations, predictions for the 160 MeV injection with high- brightness beams are delivered in terms of beam losses and emittance blow-up. These studies include the optimization of the working-point, resonance compensation and/or chromaticity correction taking into account the expected magnetic errors in the machine
32
Mann, Jennifer Erin. "Probing the potential energy surfaces of elementary neutral reactions using dissociative charge exchange." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3335027.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2008.<br>Title from first page of PDF file (viewed December 5, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Savee, John David. "An experimental probe of electronic interactions in excited molecules produced by charge exchange." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3355774.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2009.<br>Title from first page of PDF file (viewed June 25, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Martin, Lee. "Structures and properties of magnetic molecular charge transfer salts." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300630.
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Lancaster, Kelly. "Intramolecular electron transfer in mixed-valence triarylamines." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31709.
Testo completoAbstract (sommario):
Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010.<br>Committee Chair: Bredas, Jean-Luc; Committee Member: Kippelen, Bernard; Committee Member: Marder, Seth; Committee Member: Orlando, Thomas; Committee Member: Sherrill, David. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Zhou, Daming. "Modeling and Multi-Dimensional Analysis of a Proton Exchange Membrane Fuel Cell." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCA011/document.
Testo completoAbstract (sommario):
Un des freins à la commercialisation de masse de la pile à combustible et notamment de la technologie à membrane échangeuse de proton vient de sa faible durée de vie due à la difficulté de contrôler le système sous certaines conditions. Pour pallier à ce problème, l’élaboration d’un modèle mathématique précis de la pile à combustible à membrane échangeuse de protons permettant d’observer les variables internes et l'état de la pile à combustible au cours de son fonctionnement permettrait le développement de la stratégie de contrôle du système.Cette thèse propose d’élaborer un modèle dynamique multi-physique complet pour la pile à combustible à membrane échangeuse de protons. Le modèle proposé couvre les domaines multi-physiques pour les caractéristiques électriques, fluidiques et thermiques. Dans ces deux derniers domaines, les phénomènes transitoires sont notamment pris en compte dans le modèle proposé, tels que les comportements dynamiques de la teneur en eau de la membrane de la pile et la température. Par conséquent, ce modèle peut être utilisé pour analyser les effets de couplage des variables dynamiques entre différents domaines physiques.Grace à ce modèle ainsi définit, un second modèle multi-physique bidimensionnel plus détaillé est également présenté. Le modèle proposé couvre les domaines électriques et fluidiques avec une approche de modélisation 2-D innovante. Les distributions spatiales de quantité physique dans le domaine électrique peuvent ainsi être obtenues. Par conséquent, ce modèle 2-D PEMFC peut être utilisé pour étudier les influences des paramètres de modélisation sur la prédiction de performance multidimensionnelle locale. Une étude expérimentale est effectuée pour valider le modèle 2-D proposé avec une pile commerciale PEMFC Ballard NEXA de 1,2 kW.Dans un second chapitre, une analyse des phénomènes dynamiques est réalisée en fonction du modèle dynamique multidisciplinaire développé en s’appuyant sur la méthode RGA (gain relatif) pour diverses variables d'entrée de contrôle, afin d'analyser quantitativement les effets de couplage dans différents domaines physiques. L’étude s’intéresse entre autre aux interactions de la teneur en eau et de la température de la membrane. L'analyse de couplage présentée dans cette thèse peut aider les ingénieurs à concevoir et à optimiser les stratégies de contrôle des piles à combustible, en particulier pour la gestion de l'eau et de la chaleur dans les systèmes de piles à combustible.Une deuxième analyse portant sur la sensibilité aux paramètres de l'étude est effectuée sur la base du modèle multidisciplinaire bidimensionnel développé. Ces résultats d'analyse de sensibilité globale fournissent des informations utiles pour la compréhension de la dégradation, le réglage des paramètres et la simplification du modèle des piles à combustible.Dans un troisième temps, le modèle proposé se décline dans un algorithme de résolution mathématique en temps réel basé sur un algorithme de matrice tri diagonal efficace (TDMA). Les résultats expérimentaux démontrent les possibilités pratiques du modèle 2-D proposé pour le contrôle en temps réel avancé des systèmes de pile à combustible avec un temps de calcul de la boucle de contrôle de l'ordre de la milliseconde. Le temps d'exécution du modèle peut être quadruplé par rapport aux algorithme séquentiels présent dans la littérature; garantissant ainsi des décisions et des actions de contrôle rapide<br>Before mass commercialization of proton exchange membrane fuel cell, the research on the design of appropriate control strategies and auxiliaries need to be done for achieving proton exchange membrane fuel cell (PEMFC) optimal working modes. An accurate mathematical PEMFC model can be used to observe the internal variables and state of fuel cell during its operation, and could further greatly help the system control strategy development.A comprehensive multi-physical dynamic model for PEMFC is developed in chapter I. The proposed model covers multi-physical domains for electric, fluidic and thermal features. Particularly, the transient phenomena in both fluidic and thermal domain are simultaneously considered in the proposed model, such as the dynamic behaviors of fuel cell membrane water content and temperature. Therefore, this model can be used to analyze the coupling effects of dynamic variables among different physical domains.Based on the developed multi-physical PEMFC model, a full two-dimensional multi-physical model is further presented. The proposed model covers electrical and fluidic domains with an innovative 2-D modeling approach. In order to accurately describe the characteristics of reactant gas convection in the channels and diffusion through the gas diffusion layer, the gas pressure drop in the serpentine pipeline is comprehensively analyzed by fully taking the geometric form of flow field into consideration, such as the reactant gas pressure drop due to the pipeline sharp and U-bends. Based on the developed 2-D fluidic domain modeling results, spatial physical quantity distributions in electrical domain can be further obtained. Therefore, this 2-D PEMFC model can be use to study the influences of modeling parameters on the local multi-dimensional performance prediction. The simulation and experimental test are then performed to validate the proposed 2-D model with a commercial Ballard NEXA 1.2 kW PEMFC stack.In chapter II, analyses of dynamic phenomena step responses are conducted based on the developed multi-physical dynamic PEMFC model using the relative gain array (RGA) method for various control input variables, in order to quantitatively analyze the coupling effects in different physical domains, such as the interactions of membrane water content and temperature. Based on the calculated values of relative gain array, the proposed model can be considered as a fuel cell MIMO system, which could be divided into two independent control sub-systems by minimizing parameter coupling effects between each other. Due to the closely coupled parameters in the proposed first control sub-system, a decoupling control method is recommended to achieve optimized control results. The coupling analysis presented in this thesis can help engineers to design and optimize the fuel cell control strategies, especially for the water and thermal management in fuel cell systems
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Haddadian, Esmael Jafari. "Brownian dynamics study of cytochrome f / Rieske interactions with cytochrome c₆ and plastocyanin." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1123695434.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xxiii, 184 p.; also includes graphics (some col.). Includes bibliographical references (p. 169-184). Available online via OhioLINK's ETD Center
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Gunawardhana, Kihanduwage N. Gipson Stephen L. "Chemistry, electrochemistry and electron transfer induced reactions of cobalt complexes with fluorinated ligands." Waco, Tex. : Baylor University, 2007. http://hdl.handle.net/2104/5114.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Baylor University, 2007.<br>In the abstract "CF3COCo(CO)3PPh3, CF3, Bu3SnH, CF3H, [Co(CO)4]-, [Co(CO)3(PPh3)]-, C2F4, C6F5Co(CO)3PPh3, C6F5, C6F5H, C6F5D, CF3COCo(CO)3PPh3, and Co-C(acyl)" are subscript. Includes bibliographical references (p. 205-213).
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Deshpande, Abhay K. "A mechanistic evaluation of the reactions of aliphatic geminal dihalides with nucleophiles and other one electron donors." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/30314.
Testo completo
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Alrowaily, Albandari Wanes. "Deep Minima and Vortices for Positronium Formation in Positron-Hydrogen and Positron-Helium Collisions." Thesis, University of North Texas, 2021. https://digital.library.unt.edu/ark:/67531/metadc1808421/.
Testo completoAbstract (sommario):
This dissertation work is a study of positronium formation for positron-hydrogen and positron-helium collisions in the Ore gap (the energy region between the threshold for ground-state positronium formation and the first excitation level of the target atom) using variational K-matrices. We have fitted the K-matrices using multichannel effective range theories and using polynomials. Using the variational K-matrices and their fits, we have located zeros in the positronium-formation scattering amplitude and corresponding deep minima in the positronium-formation differential cross section. The zeros are related to the vortices in the extended velocity field associated with the positronium-formation scattering amplitude. For positron-hydrogen collisions, we have found two zeros in the positronium-formation scattering amplitude, and corresponding deep minima in the positronium-formation differential cross section, while we have obtained a zero in the positronium-formation scattering amplitude for positron-helium collisions. We have connected the zeros in the positronium-formation scattering amplitude to vortices in the extended velocity fields. Our work shows that vortices can occur for charge exchange in atomic collisions.
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Sathiosatham, Muhunthan. "The synthesis and noncovalent electron-transfer studies of anthracene and dimethylaniline substituted nucleic acid bases and G-quartet formation in the absence of templating metal ions." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992906.
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Zhang, Yulin. "Substrate recognition by holocytochrome C synthase in cytochrome C biogenesis system III." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:47533f13-92c5-4349-8b70-02e659a00112.
Testo completoAbstract (sommario):
C-type cytochromes are ubiquitous proteins with crucial functions in organisms, which include electron transfer and apoptotic signalling. In eukaryotic organisms, mitochondrial cytochrome c is located in the intermembrane space, and it is a component of the electron transport chain; it is responsible for transferring electrons from Complex III to Complex IV. The regulated release of cytochrome c from mitochondria results in the activation of a signal transduction pathway leading to controlled cell death, or apoptosis. In mitochondrial c-type cytochromes, the heme is bound to both cysteines of a CXXCH motif located near the N-terminus. The covalent heme attachment in c-type cytochromes, the final step in its biosynthesis, is achieved by different cytochrome c biogenesis systems in different organisms. Out of these systems, System III, found in many eukaryotes, has a single component - holocytochrome c synthase (HCCS) which is the enzyme responsible for the catalysis of heme binding to cytochrome c. HCCS recognises apocytochrome c as a substrate upon the import of the apocytochrome from the cytosolic space to the mitochondrial intermembrane space. The requirements of amino acid sequence for HCCS recognition had remained an intriguing question, despite the relatively long period since the discovery of the enzyme. Thus, HCCS in System III and its substrate recognition is the subject of this thesis. This thesis describes the experiments showing that the N-terminal region of the mitochondrial cytochrome c protein is important for substrate recognition, as well as further characterisation of this sequence by mutagenesis. Out of several highly conserved residues in the N-terminus, a phenylalanine residue in the N-terminus is identified to be critical for heme attachment by HCCS. The role of this phenylalanine residue in the interaction between the two proteins was probed by substituting it with a range of residues. Furthermore, the importance of the spacing between the key phenylalanine residue and the CXXCH motif was investigated. A single-cysteine variant of the mitochondrial cytochrome c with a single bond to the heme is produced by HCCS, but heme attachment only occurs if histidine is present as an axial ligand to the heme iron. Replacement of the histidine with other potential iron-ligating residues abolished heme attachment. These results bring insight into the critical features in amino acid sequence of cytochrome c for the substrate recognition specificity of HCCS. Sequence analysis on the N-terminal region of mitochondrial cytochromes c in a variety of organisms reveals evolutionary implications for cytochrome c biogenesis systems. It also attempts to explain the reason for negative results in previous chapters for the analysis of the N-terminal region of cytochrome c. An improved method for human HCCS production is also described in this thesis, for the exploitation of purification and characterisation in future studies of HCCS.
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Miller, Jody Christopher. "Calibration and parametric study of the Alcator C-Mod charge exchange neutral particle analyzers." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38366.
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Latacz, Barbara Maria. "Study of the antihydrogen atom and ion production via charge exchange reaction on positronium." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS266/document.
Testo completoAbstract (sommario):
Le but principal de la collaboration GBAR est de mesurer le comportement d'atomes d'antihydrogène sous l'effet de la gravité terrestre. Ceci est fait en mesurant la chute libre classique d'atomes d'antihydrogène, qui est un test direct du principe d'équivalence faible pour l'antimatière. La première étape de l'expérience est de produire des ions d'antihydrogène et de les amener dans un piège de Paul, où ils peuvent être refroidis à une température de l'ordre du μK en utilisant la technique du refroidissement sympathique avec des ions Be⁺ eux-mêmes mis dans leur état fondamental par la technique Raman à bande latérale. Une température de l'ordre du μK correspond à une vitesse de la particule de l'ordre de 1 m/s. Une fois cette vitesse atteinte, l'ion antihydrogène peut être neutralisé et commence sa chute. Ceci permet une précision de 1 % sur la mesure de l’accélération gravitationnelle g pour l’antimatière avec environ 1500 événements. Cependant, pour mesurer la chute libre, il faut d'abord produire l'ion antihydrogène. Celui-ci est formé dans les réactions d'échange de charge entre des antiprotons et des antihydrogènes avec du positronium. Positronium et atomes d'antihydrogène peut se trouver soit à l’état fondamental, soit dans un état excité. Une étude expérimentale de la mesure de la section efficace de ces deux réactions est décrite dans cette thèse. La production de l'atome d'antihydrogène ainsi que de l'ion se passe à l’intérieur d'une cavité. La formation d'un antihydrogène ion lors d'une interaction entre faisceaux requiert environ 5x10⁶ antiprotons/paquet et quelques 10¹¹ Ps/cm⁻³ de densité de positronium à l’intérieur d'une cavité. Celle-ci est produite par un faisceau contenant 5x10¹⁰ positrons par paquet. La production de faisceaux aussi intenses avec les propriétés requises est en soi un challenge. Le développement de la source de positrons de GBAR est décrite. Celle-ci est basée sur un accélérateur linéaire à électrons de 9 MeV. Le faisceau d’électrons est incident sur une cible de tungstène où les positrons sont créés par rayonnement de freinage (gammas) et création de paires. Une partie des positrons ainsi créés diffusent à nouveau dans un modérateur de tungstène en réduisant leur énergie à environ 3 eV. Ces particules sont re-accélérées à une énergie d'environ 53 eV. Aujourd'hui, le flux mesuré de positrons est au niveau de 6x10⁷ e⁺/s, soit quelques fois. Puis la thèse comporte une courte description des préparatifs pour les faisceaux d'antiprotons ou de protons, terminée par un chapitre sur le taux de production attendu d'atomes et d'ions d'antihydrogène. En aval de la réaction, les faisceaux d'antiprotons, d'atomes et d'ions d'antihydrogène sont guidés vers leur système de détection. Ceux-ci ont été conçus de façon à permettre la détection d'un à plusieurs milliers d'atomes d'antihydrogène, un seul ion antihydrogène et tous les 5x10⁶ antiprotons. Ceci est particulièrement difficile parce que l'annihilation des antiprotons crée beaucoup de particules secondaires qui peuvent perturber la mesure d'un atome ou ion. La majeure partie de la thèse consiste en la description des bruits de fond attendus pour la détection des atomes et ions d'antihydrogène. De plus, le système de détection permet de mesurer les sections efficaces pour les réactions symétriques de production d'atomes et d'ions hydrogèene par échange de charge entre protons et positronium. La partie production d’antihydrogène ions de l’expérience a été complètement installée au CERN en 2018. Les premiers tests avec des antiprotons provenant du décélérateur ELENA ont été effectués. Actuellement, l’expérience est testée avec des positrons et des protons, de façon à former des atomes et ions hydrogène. Une optimisation de la production de ces ions de matière aidera à se préparer pour la prochaine période de faisceau d'antiprotons en 2021<br>The main goal of the GBAR collaboration is to measure the Gravitational Behaviour of Antihydrogen at Rest. It is done by measuring the classical free fall of neutral antihydrogen, which is a direct test of the weak equivalence principle for antimatter. The first step of the experiment is to produce the antihydrogen ion and catch it in a Paul trap, where it can be cooled to μK temperature using ground state Raman sideband sympathetic cooling. The μK temperature corresponds to particle velocity in the order of 1 m/s. Once such velocity is reached, the antihydrogen ion can be neutralised and starts to fall. This allows reaching 1 % precision on the measurement of the gravitational acceleration g for antimatter with about 1500 events. Later, it would be possible to reach 10⁻⁵ - 10⁻⁶ precision by measuring the gravitational quantum states of cold antihydrogen. However, in order to measure the free fall, firstly the antihydrogen ion has to be produced. It is formed in the charge exchange reactions between antiproton/antihydrogen and positronium. Positronium and antihydrogen atoms can be either in a ground state or in an excited state. An experimental study of the cross section measurement for these two reactions is described in the presented thesis. The antihydrogen atom and ion production takes place in a cavity. The formation of one antihydrogen ion in one beam crossing requires about 5x10⁶ antiprotons/bunch and a few 10¹¹ Ps/cm⁻³ positronium density inside the cavity, which is produced with a beam containing 5x10¹⁰ positrons per bunch. The production of such intense beams with required properties is a challenging task. First, the development of the positron source is described. The GBAR positron source is based on a 9 MeV linear electron accelerator. The relatively low energy was chosen to avoid activation of the environment. The electron beam is incident on a tungsten target where positrons are created from Bremsstrahlung radiation (gammas) through the pair creation process. Some of the created positrons undergo a further diffusion in the tungsten moderator reducing their energy to about 3 eV. The particles are re-accelerated to about 53 eV energy and are adiabatically transported to the next stage of the experiment. Presently, the measured positron flux is at the level of 6x10⁷ e⁺/s, which is a few times higher than intensities reached with radioactive sources. Then, the thesis features a short description of the antiproton/proton beam preparations, finalised with a chapter about the expected antihydrogen atom and ion production yield. After the reaction, antiproton, antihydrogen atom, and ion beams are guided to the detection system. It is made to allow for detection from 1 to a few thousand antihydrogen atoms, a single antihydrogen ion and all 5x10⁶ antiprotons. It is especially challenging because antiproton annihilation creates a lot of secondary particles which may disturb measurements of single antihydrogen atoms and ions. The main part of the Thesis is the description of the expected background for the antihydrogen atom and ion detection. Additionally, the detection system allows measuring the cross sections for the symmetric reactions of a hydrogen atom and ion production through charge exchange between protons and positronium. The antihydrogen ion production part of the experiment was fully installed at CERN in 2018. The first tests with antiprotons from the ELENA decelerator were done. Currently, the experiment is being commissioned with positrons and protons, in order to perform the hydrogen atom and ion formation. The optimisation of the ion production with matter will help to be fully prepared for the next antiproton beam time in 2021
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曾俊傑 and Chun-kit Tsang. "Pathway analysis on electron transfer in ruthenium modified cytochromeC." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31225226.
Testo completo
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Xu, Shujuan. "EPR studies of electron and proton transfer in cytochrome c oxidase." Diss., Connect to online resource - MSU authorized users, 2008.
Cerca il testo completoAbstract (sommario):
Thesis (Ph. D.)--Michigan State University. Chemistry, Biochemistry and Molecular Biology, 2008.<br>Title from PDF t.p. (viewed on July 2, 2009) Includes bibliographical references. Also issued in print.
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Eaton, Brandon Michael. "One Dimensional, Transient Model of Heat, Mass, and Charge Transfer in a Proton Exchange Membrane." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32788.
Testo completoAbstract (sommario):
A transient, one-dimensional, model of the membrane of a proton exchange membrane fuel cell is presented. The role of the membrane is to transport protons from the anode to cathode of the fuel cell while preventing the transport of other reactants. The membrane is modeled assuming mono-phase, multi-species flow. For water transport, the principle driving forces modeled are a convective force, an osmotic force (i.e. diffusion), and an electric force. The first of these results from a pressure gradient, the second from a concentration gradient, and the third from the migration of protons from anode to cathode and their effect (drag) on the dipole water molecules. Equations are developed for the conservation of protons and water, the conservation of thermal energy, and the variation of proton potential within the membrane.
The model is solved using a fully implicit finite difference approach. Results showing the effects of current density, pressure gradients, water and heat fluxes, and fuel cell start-up on water concentration, temperature, and proton potential across the membrane are presented.<br>Master of Science
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Eissa, Farhat. "Charge exchange laboratory studies relevant to solar-wind-induced cometary and planetary x-ray emission /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3276956.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Nevada, Reno, 2007.<br>Includes bibliographical references (leaves 95-99). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Claypool, Ian Randolph. "A theoretical and numerical study of the use of grid embedded axial magnetic fields to reduce charge exchange ion induced grid erosion in electrostatic ion thrusters." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1172690635.
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Odom, Susan A. "Electron transfer and delocalization in mixed-valence monocations of bis- and tris-(diarylamino) derivatives." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26609.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.<br>Committee Chair: Marder, Seth; Committee Member: Bredas, Jean-Luc; Committee Member: Collard, David; Committee Member: Kippelen, Bernard; Committee Member: Tolbert, Laren. Part of the SMARTech Electronic Thesis and Dissertation Collection.